Method for manufacturing fuel cell electrolyte film-electrode bond

ABSTRACT

In order to obtain an electrolyte membrane-electrode assembly using a thin electrolyte membrane, the present invention provides a production method of an electrolyte membrane-electrode assembly comprising: a step of forming a hydrogen ion-conductive polymer electrolyte membrane on a base material; a treatment step of reducing adhesion force between the base material and the hydrogen ion-conductive polymer electrolyte membrane; a step of separating and removing the base material; and a step of bonding a catalyst layer and a gas diffusion layer onto the hydrogen ion-conductive polymer electrolyte membrane, and, in order to obtain an electrolyte membrane-electrode assembly which has a catalyst without clogging and is excellent in electrode characteristics, the present invention provides a production method of an electrolyte membrane-electrode assembly comprising: a step of bonding a hydrogen ion-conductive polymer electrolyte membrane and a catalyst layer via a coating layer; a step of removing the coating layer; and a step of obtaining an electrolyte membrane-electrode assembly by forming a gas diffusion layer on the catalyst layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Section 371 of International Application No.PCT/JP02/00257, filed Jan. 16, 2002, the disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electrolyte membrane-electrodeassembly used for a polymer electrolyte fuel cell.

BACKGROUND ART

An electrolyte membrane-electrode assembly used for a polymerelectrolyte fuel cell (PEFC) is obtained by bonding a first gasdiffusion electrode as an anode and a second gas diffusion electrode asa cathode to a film-shaped hydrogen ion-conductive polymer electrolytemembrane as an electrolyte. The gas diffusion electrode is composed of agas diffusion layer and a catalyst layer, and the gas diffusion layer isconstituted of porous carbon paper or the like. The catalyst layers ofthe anode and cathode are constituted of noble metal fine particles andcarbon particles carrying these fine particles thereon.

As shown in FIG. 10(b), an electrolyte membrane-electrode assembly forthe PEFC is obtained by bonding gas diffusion electrodes 146 and 147 toa film-shaped polymer electrolyte membrane 141 as the electrolyte. Thepolymer electrolyte membrane 141 is typically supplied with a roll.

FIG. 10(a) shows one example of production methods of the electrolytemembrane-electrode assembly, and herein, carbon paper (gas diffusionlayers) 142 and 144 with catalyst layers 143 and 145 formed thereon arepress-contacted with the polymer electrolyte membrane 141 by hotpressing. Another method is to form the catalyst layer on the polymerelectrolyte membrane in advance by transfer-printing, printing or thelike, and carbon paper is then press-contacted therewith.

In the catalyst layer 143 on the anode side, a reaction represented bythe formula (1) occurs:H₂→2H⁺+2e⁻  (1),while, in the catalyst layer 145 on the cathode side, a reactionrepresented by the formula (2) occurs:½O₂+2H⁺+2e⁻→H₂O  (2)When the above reactions occur, protons (hydrogen ions) generated in theanode migrate to the cathode through the polymer electrolyte membrane141.

Such a PEFC is required to generate a high output voltage, for which itis of necessity for a polymer electrolyte membrane used to have highproton conductivity, namely, to have low internal resistance. In orderto obtain high proton conductivity, there are needs for the use of amaterial with high proton conductivity for the polymer electrolytemembrane and for the use of as thin a membrane as possible.

For a polymer electrolyte membrane in a typical PEFC used has been apolymer electrolyte membrane made of perfluorocarbon sulfonic acidionomer, represented by Nafion 112 produced by Du Pont in the US, and amembrane having a thickness of about 30 to 50 μm has been put topractical use.

A polymer electrolyte membrane made of perfluorocarbon sulfonic acidionomer which has higher proton conductivity than aforesaid Nafion mayby exemplified by a Flemion S H membrane produced by Asahi Glass Co.,Ltd.; however, there is a problem with this membrane that the membraneis more fragile and breakable than Nafion 112 because of containment ofthe sulfonic acid group therein. A membrane in practical use thereforehas a thickness of not less than about 50 μm.

In order to make the polymer electrolyte membrane thinner, for example,Japanese Laid-Open Patent Publication No. Hei 08-162132 discloses amethod in which a porous cloth made of polytetrafluoroethylene is usedas a core member and in the porous part thereof, a polymer electrolyteresin is impregnated so as to form a polymer electrolyte membraneimparted with high intensity.

The examples of specific products produced by this method may include aGORE-SELECT membrane produced by JAPAN GORE-TEX INC. This type ofmembrane with a thickness of as thin as about 20 to 30 μm has been inpractical use by using a reinforcing material.

Next, as for the production method of the electrolyte membrane-electrodeassembly, there is a method in which an ink-like or paste-like mixtureof the catalyst and the electrolyte, containing the catalyst, is appliedonto the surface of the electrolyte membrane or of the gas diffusionlayer by printing, spraying or the like. In either method, afterapplication of the mixture, the electrolyte membrane and the gasdiffusion electrode are bonded to each other by hot pressing or the like(e.g., Japanese Laid-Open Patent Publication No. Hei 6-203849, JapaneseLaid-Open Patent Publication No. Hei 8-88011 and Japanese Laid-OpenPatent Publication No. Hei 8-106915.)

There is another production method of the electrolyte membrane-electrodeassembly, in which the catalyst layer formed on the base material inadvance is transfer-printed to the electrolyte membrane by hot pressingor thermoroll (e.g., Japanese Laid-Open Patent Publication No. Hei10-64574). This method is excellent from the viewpoints of control onand uniformity of the film thickness of the catalyst layer, productionefficiency and cell performance.

However, the conventional production method comprises a step of handlingthe electrolyte membrane without using the base material for theelectrolyte membrane. Thereby, when the electrolyte membrane with a filmthickness less than 20 μm and lower intensity is used, for example, ithas been extremely difficult to produce the electrolytemembrane-electrode assembly without breakage of the electrolytemembrane.

That is to say, when drawing stress or sheering stress is directlyapplied to the electrolyte membrane with a thin film thickness in thestate that the base material for the electrolyte membrane is not presentin the process of producing the electrolyte membrane-electrode assembly,defects such as a pinhole, breakage and crack easily occur. Thesedefects cause occurrence of crossover of a fuel gas and air or ofshort-circuit in the electrolyte membrane-electrode assembly, raising aproblem of significant deterioration of performance of the PEFC.

Moreover, since the polymer electrolyte having high proton conductivitysuch as perfluorocarbon sulfonic acid ionomer contains a hydrophilicgroup such as the sulfonic acid group in the molecular chain, ionomersoluble to water tends to gradually flow into the gas diffusion layersuch as carbon paper in operation of the fuel cell. For this reason,there has been a problem that a reaction area of a triphasic interface,formed of a pore as a supply channel of a reaction gas, a polymerelectrolyte having proton conductivity due to containment of water andan electrode material as an electron conductor, gradually becomessmaller, decreasing cell output. Further, there has been another problemthat, when a current collector having a gas flow channel arranged in theoutside of the assembly of the polymer electrolyte membrane and theelectrode is made of metal, the assembly is gradually corroded withdissolved acidic ionomer, significantly lowering reliability of the fuelcell.

In order to solve the above problems, therefore, it is an object of thepresent invention to provide an electrolyte membrane-electrode assemblyfor a polymer electrolyte fuel cell with low internal resistance and ofgreat power, which can use perfluorocarbon sulfonic acid ionomer havinghigh proton conductivity and comprises a thin polymer electrolytemembrane capable of being formed on a catalyst layer.

It is also an object of the present invention to provide an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell, whichhas a uniform film thickness to cause no clogging in the porous part ofthe catalyst layer of the gas diffusion electrode by preventing soakageof the raw material solution of the polymer electrolyte membrane intothe porous part, thereby having excellent electrode properties.

It is further an object of the present invention to provide anelectrolyte membrane-electrode assembly using a polymer electrolytehaving high proton conductivity and exhibiting excellent durability andhigh performance, and a polymer electrolyte fuel cell constituted usingthis assembly.

DISCLOSURE OF INVENTION

The present invention relate to a production method of an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell,comprising: a gas diffusion electrode having a gas diffusion layer and acatalyst layer; and a hydrogen ion-conductive polymer electrolytemembrane bonded to the gas diffusion electrode, the method beingcharacterized by comprising: a step of forming a hydrogen ion-conductivepolymer electrolyte membrane on a base material; a treatment step ofreducing adhesion force between the base material and the hydrogenion-polymer electrolyte membrane; a step of separating and removing thebase material; and a step of bonding a catalyst layer and a gasdiffusion layer onto the hydrogen ion-conductive polymer electrolytemembrane.

It is preferable that the production method comprises a step oftransfer-printing a membrane at least one time and the hydrogenion-conductive polymer electrolyte membrane is supported by the basematerial until an electrolyte membrane-electrode assembly is obtained.

It is also preferable that the production method comprises: a step (1)of forming a hydrogen ion-conductive polymer electrolyte membrane on afirst base material and a second base material; a step (2) of forming acatalyst layer on the hydrogen ion-conductive polymer electrolytemembrane formed on the base material; a step (3) of attaching bypressure and bonding a gasket and a gas diffusion layer onto thehydrogen ion-conductive polymer electrolyte membrane and the catalystlayer on the base material; a step (4) of separating and removing thebase material to obtain a first semi-assembly and a second-semiassembly; and a step (5) of attaching by pressure the firstsemi-assembly to the second semi-assembly while the hydrogenion-conductive polymer electrolyte membranes thereof are mutuallyopposed to obtain an electrolyte membrane-electrode assembly, and themethod further comprises, between the steps (1) and (4), a treatmentstep of reducing adhesion force between the base material and thehydrogen ion-conductive polymer electrolyte membrane.

It is also preferable that the production method comprises: a step (I)of forming a catalyst layer on a first base material and a second basematerial; a step (II) of forming a hydrogen ion-conductive polymerelectrolyte membrane on the catalyst layer such that the membrane coversthe catalyst layer formed on the base material and on the periphery ofthe catalyst layer; a step (III) of attaching by pressure the first basematerial to the second base material while the hydrogen ion-conductivepolymer electrolyte membranes thereof are mutually opposed to obtain apre-assembly; a step (IV) of separating and removing the first basematerial from the pre-assembly; a step (V) of attaching by pressure agas diffusion layer and a gasket onto the catalyst layer and thehydrogen ion-conductive polymer electrolyte membrane which are exposedby the step (IV); a step (VI) of separating and removing the second basematerial from the pre-assembly; and a step (VII) of attaching bypressure a gas diffusion layer and a gasket onto the catalyst layer andthe hydrogen ion-conductive polymer electrolyte membrane which areexposed by the step (VI) to obtain an electrolyte membrane-electrodeassembly, and the method comprises, between the steps (II) and (IV)and/or between the steps (IV) and (VII), a treatment step of reducingadhesion force between the base material and the hydrogen ion-conductivepolymer electrolyte membrane.

It is also preferable that the step of forming a hydrogen ion-conductivepolymer electrolyte membrane on a base material is a step oftransfer-printing a hydrogen ion-conductive polymer electrolyte membraneformed on a base material for transfer-printing, to the base material.

It is also preferable that the surface or the whole of the base materialis constituted of a material which reduces the adhesion property to thehydrogen ion-conductive polymer electrolyte membrane by heating, or amaterial which evaporates or sublimates by heating, and the treatmentstep is a step of heating the base material.

It is also preferable that the surface or the whole of the base materialis constituted of a material which reduces the adhesion property to thehydrogen ion-conductive polymer electrolyte membrane by cooling, and thetreatment step is a step of cooling the base material.

It is also preferable that the surface or the whole of the base materialis constituted of a material which reduces the adhesion property to thehydrogen ion-conductive polymer electrolyte membrane by irradiatingactive light rays, or a material which evaporates or sublimates byirradiating active light rays, and the treatment step is a step ofirradiating the base material with active light rays.

It is further preferable that the base material comprises on the surfacethereof an adhesion layer capable of dissolving in a solvent, and thetreatment step is a step of bringing the base material in contact with asolvent.

It is also preferable that the treatment step is a step ofdepressurizing or pressurizing the face of the base material opposite tothe face thereof with the hydrogen ion-conductive polymer electrolytemembrane formed.

It is further preferable that the production method comprises a step ofarranging a reinforcing film made of a frame-shaped hydrogenion-conductive film or gas diffusive film, between the hydrogenion-conductive polymer electrolyte membrane and the catalyst layer,between the catalyst layer and the gas diffusion layer or between thehydrogen ion-conductive polymer electrolyte membranes, in a clearancebetween the gasket and the gas diffusion electrode in order to reinforcethe hydrogen ion-conductive polymer electrolyte membrane.

The present invention further relates to a production method of anelectrolyte membrane-electrode assembly for a polymer electrolyte fuelcell, the electrolyte membrane-electrode assembly having: a hydrogenion-conductive polymer electrolyte membrane; and a gas diffusionelectrode which contains a catalyst layer and a gas diffusion layer andis bonded to both faces of the hydrogen ion-conductive polymerelectrolyte membrane, the method being characterized by comprising: astep of bonding a hydrogen ion-conductive polymer electrolyte membraneand a catalyst layer via a coating layer; a step of removing the coatinglayer; and a step of obtaining an electrolyte membrane-electrodeassembly by forming a gas diffusion layer on the catalyst layer.

It is preferable that the method comprises: a step (a1) of forming acoating layer on a catalyst layer; a step (b1) of applying a hydrogenion-conductive polymer electrolyte solution onto the coating layer; astep (c1) of removing the coating layer to obtain an electrolytemembrane-catalyst layer assembly; and a step (d1) of forming a gasdiffusion layer on the catalyst layer.

It is preferable that the production method comprises: a step (a2) offorming a hydrogen ion-conductive polymer electrolyte membrane on apolymer film; a step (b2) of arranging a catalyst layer on the polymerfilm; a step (c2) of removing the polymer film to obtain an electrolytemembrane-catalyst layer assembly; and a step (d2) of forming a gasdiffusion layer on the catalyst layer.

It is also preferable that the method comprises: a step (a3) of forminga coating layer containing a hydrogen ion-conductive polymer electrolyteon a catalyst layer; a step (b3) of applying a hydrogen ion-conductivepolymer electrolyte solution onto the coating layer; a step (c3) ofremoving the coating layer to obtain an electrolyte membrane-catalystlayer assembly; and a step (d3) of forming a gas diffusion layer on thecatalyst layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical sectional view representing a step of forming anelectrolyte membrane and a step of forming a catalyst layer inaccordance with one embodiment of the present invention.

FIG. 2 is a vertical sectional view representing steps subsequent to thesteps in FIG. 1 until separation and removal of a base material for theelectrolyte membrane.

FIG. 3 is a vertical sectional view representing steps subsequent to thesteps in FIG. 2 until constitution of an electrolyte membrane-electrodeassembly.

FIG. 4 is a vertical sectional view representing steps from formation ofthe catalyst layer to separation and removal of one electrolyte membranebase material in another embodiment of the present invention.

FIG. 5 is a vertical sectional view representing steps subsequent to thesteps in FIG. 4 until separation and removal of the other electrolytemembrane base material.

FIG. 6 is a vertical sectional view representing steps subsequent to thesteps in FIG. 5 until constitution of an electrolyte membrane-electrodeassembly.

FIG. 7 is a vertical sectional view representing the production processof the electrolyte membrane-electrode assembly for a fuel cell inExample 3.

FIG. 8 is a vertical sectional view representing the production processof the electrolyte membrane-electrode assembly for a fuel cell inExample 4.

FIG. 9 is a vertical sectional view representing the production processof the electrolyte membrane-electrode assembly for a fuel cell inExample 5.

FIG. 10 is a vertical sectional view representing the production processof the electrolyte membrane-electrode assembly for a fuel cell inComparative Example 2.

FIG. 11 is a vertical sectional view representing the production processof the electrolyte membrane-electrode assembly for a fuel cell inComparative Example 3.

FIG. 12 is a diagram conceptually representing the interaction ofionomer and bifunctional amine in the catalyst layer of the electrolytemembrane-electrode assembly in Reference Example 1 of the presentinvention.

FIG. 13 is a diagram conceptionally representing the interaction ofionomer and the basic functional group on the carbon fine powder in thecatalyst layer of the electrolyte membrane-electrode assembly inReference Example 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(1) First Production Method:

The present invention firstly relates to a production method of anelectrolyte membrane-electrode assembly for a polymer electrolyte fuelcell, comprising: a gas diffusion electrode having a gas diffusion layerand a catalyst layer; and a hydrogen ion-conductive polymer electrolytemembrane bonded to the gas diffusion electrode, characterized bycomprising: a step of forming a hydrogen ion-conductive polymerelectrolyte membrane on a base material for the electrolyte membrane(hereinafter also referred to as, simply, “base material”); a treatmentstep of reducing adhesion force between the base material and thehydrogen ion-polymer electrolyte membrane; a step of separating andremoving the base material; and a step of bonding a catalyst layer and agas diffusion layer onto the hydrogen ion-conductive polymer electrolytemembrane.

According to the present invention, even when an electrolyte membranewith a thin film thickness is used, it is possible to produce theelectrolyte membrane-electrode assembly without breakage of theelectrolyte membrane.

First, in the production method of the present invention, theelectrolyte membrane is formed on the base material either by formingthe electrolyte membrane directly on the base material by a solventcasting method or the like or by transfer-printing the electrolytemembrane produced on the base material for transfer-printing onto thebase material for the electrolyte membrane. The electrolyte membrane canthereby be handled in the state of being carried by the base material,from a step of forming the electrolyte membrane through a step ofbonding and integrating the base material having the electrolytemembrane and the catalyst layer formed on the electrolyte membrane, andcell members including a gas diffusion layer and a gasket.

Furthermore, in a step of separating and removing the base material fromthe assembly of the cell members and the base material with theelectrolyte-catalyst layer formed, each of the cell members attached bypressure serves to support and protect the electrolyte membrane. Also ina step of producing an electrolyte membrane-electrode assembly with ananode and a cathode arranged by attaching by pressure the respectiveelectrolyte membranes of the two semi-assemblies of the electrolytemembrane and the electrode as thus constituted (a first semi-assemblyand a second semi-assembly) to each other, each of the cell members thusattached by pressure plays the role of the base material in protectingthe electrolyte membrane.

Moreover, in the production method of the present invention, afterformation of the catalyst layer on the base material, the electrolytemembrane is formed on the catalyst layer and on the base material beingon the periphery of the catalyst layer. Subsequently, the respectivefaces on the electrolyte membrane side of the two base materials, onwhich the catalyst layer and the electrolyte membrane have been formed,are mutually opposed to be attached by pressure to each other so as toform an assembly. In each of these steps, each electrolyte membrane ishandled as being supported by the base material. One base material isthen separated and removed from this assembly and the cell membersincluding the gas diffusion layer and the gasket are bonded to the faceon the catalyst layer side exposed due to the separation and removal. Ineach of these steps, each electrolyte membrane is supported by the otherbase material. After attachment by pressure of the cell members, in eachof the steps from separation and removal of the other base material tocompletion of the polymer membrane electrode assembly, each of the cellmembers thus attached by pressure serves to support and protect theelectrolyte membrane.

In this manner, according to the production method of the presentinvention, the electrolyte membrane is at all times protected by thebase material, or the base material for transfer-printing or the cellmembers, which have the corresponding role to the base material. Even ina case where an electrolyte membrane with weak mechanical strength byreason that the film thickness thereof is thin or the like is used,accordingly, an electrolyte membrane-electrode assembly and a PEFC usingthe same can be produced without causing damage to the electrolytemembrane. Namely, according to the present invention, because stressapplied to the electrolyte membrane by printing, transfer-printing, hotpressing or the like in the production process of the electrolytemembrane-electrode assembly is absorbed by the base material, the cellmembers playing the corresponding role to the base material or the like,large stress is not applied to the electrolyte membrane, and hence doesnot cause damage to the electrolyte membrane even when it is with lawintensity.

In the production method of the present invention, at least anywherebetween the step of forming the electrolyte membrane on the basematerial and the step of separating and removing the base material,between the step of forming the electrolyte membrane and the step ofseparating and removing one base material, and between the step ofseparating and removing one base material and the step of separating andremoving the other base material, it is necessary to conduct a treatmentstep for decreasing adhesion force between the base material and theelectrolyte membrane. As for such a treatment step, effective treatmentsteps may include, for example, irradiation of active light rays such asultraviolet rays, X-rays, gamma rays or electron rays, heating, cooling,contact with a solvent or application of a pressure difference by theuse of vapor.

(i) Embodiment 1

Embodiment 1 for the production method of an electrolytemembrane-electrode assembly in the present invention will be describedby means of FIGS. 1 to 3: FIG. 1 shows steps of sequentially forming anelectrolyte membrane 2 and a catalyst layer 6 on a base material 3.First, a hydrogen ion-conductive polymer electrolyte solution is appliedto a base material 1 for transfer-printing with a coater, followed bydrying, to form the electrolyte membrane 2 on the base material 1 forprint-transfer, as in FIG. 1(a). Subsequently, as in FIG. 1(b), theother base material 3 capable of decreasing adhesion force of thesurface is attached by pressure to the electrolyte membrane 2 on thebase material 1 for transfer-printing with a laminating machine 4 suchthat the air does not get in the respective bonding parts. Next, as inFIG. 1(c), the base material 1 for transfer-printing is separated andremoved from the electrolyte membrane 2, and the electrolyte membrane 2is transfer-printed onto the base material 3.

Further, as in FIG. 1(d), the electrolyte membrane 2 transfer-printedonto the base material 3 and a catalyst layer 6 formed on the basematerial 5 for the catalyst layer are piled to be attached by pressureto each other with the use of a hot pressing machine 7. The basematerial 5 for the catalyst layer is then separated from the catalystlayer 6, and as in FIG. 1(e), the catalyst layer 6 is transfer-printedonto the electrolyte membrane 2. As thus described, since theelectrolyte membrane 2 is supported by the base material 1 fortransfer-printing in the steps of FIGS. 1(a) and (b) and it is supportedby the base material 3 for the electrolyte membrane in each of the stepsFIGS. 1(c) to (e), it should not sustain damage.

While FIG. 1 shows the example of forming the electrolyte membrane 2 bythe transfer-printing method, it is also possible to form theelectrolyte membrane 2 directly on the base material 3 by a solventcasting method in which an electrolyte solution is applied onto the basematerial 3, followed by drying.

Next, FIG. 2 shows steps from formation of the catalyst layer 6 on theelectrolyte membrane 2 to separation and removal of the base material 3from the electrolyte membrane 2. First, as in FIG. 2(a), ultravioletrays are irradiated with an ultraviolet lamp 8 from the back face of thebase material 3 on which the electrolyte membrane 2 and the catalystlayer 6 have been formed. By a treatment step such as ultravioletirradiation, it is possible to get rid of most of the adhesion forcebetween the electrolyte membrane 2 and the base material 3 generated informing the electrolyte membrane 2 on the base material 3 by thetransfer-printing method, the solvent casting method or the like.

Then, as in FIG. 2(b), a gas diffusion layer 10 repellent-treated inadvance, a gasket 9 and a hydrogen ion-conductive film 11 are arrangedon the base material-electrolyte membrane-catalyst layer assembly havingbeen irradiated with ultraviolet rays and then these materials areattached by pressure with the use of a hot pressing machine 12 to beintegrated as in FIG. 2(c). In the above steps of FIGS. 2(a) to (c), theelectrolyte membrane 2 sustains no damage as being supported by the basematerial 3. Thereafter, the base material 3 is separated from the basematerial 2 as in FIG. 2 (d) to obtain a semi-assembly 13 of theelectrolyte membrane and the electrode.

In the step of FIG. 2(d), the electrolyte membrane 2 adheres to the cellmembers including the gas diffusion layer 10, the gasket 9 and thehydrogen ion-conductive film 11 processed to be frame-shaped, to beintegrated. For this reason, stress applied to the base material 2 inseparating the base material 3 is alleviated by these cell members. Asthus described, in addition to support and protection for the basematerial 2 by these cell members, adhesion force to the base material 3has been decreased by the aforesaid treatment step, thereby facilitatingseparation of the base material 3 without causing any damage to theelectrolyte membrane 2 to obtain the semi-assembly 13 of the electrolytemembrane-electrode.

Even when the aforesaid treatment for decreasing adhesion force isconducted on the base material 3 with the electrolyte membrane 2 and thecatalyst layer 6 formed thereon as in FIG. 2(a), or even when thetreatment is conducted, for example, on the base material 3 after beingintegrated with the cell members as in FIG. 2(c), the similar effectscan be obtained. A gas diffusive film may be used in place of thehydrogen ion-conductive film 11. When the gas diffusion layer 10 and thegasket 9 as the cell members are attached by pressure to the basematerial-electrolyte membrane-catalyst layer assembly, the electrolytemembrane 2 is almost thoroughly supported by these materials.Simultaneous attachment by pressure of the hydrogen ion-conductive film11 or the gas diffusive film results in an increased effect ofprotecting the electrolyte membrane, especially in the vicinity of thegap between the gasket and the gas diffusion electrode.

FIG. 3 shows steps of producing an electrolyte membrane-electrodeassembly by integrating the first semi-assembly 13 of the electrolytemembrane-electrode and a second semi-assembly 14 without the hydrogenion-conductive film 11 being attached by pressure thereto as thusproduced. The respective electrolyte membranes 2a and 2b of thesemi-assemblies 13 and 14 are mutually opposed as in FIG. 3(a), whichare then attached by pressure to each other with the use of a hotpressing machine 15 as in FIG. 3(b). Thereby, the electrolytemembrane-electrode assembly as shown in FIG. 3(c) can be obtained.Further, the assembly is stood still in a depressurized container for 10minutes for deaeration of the assembly.

In the aforesaid case, two of the semi-assemblies 14 without hydrogenion-conductive film 11 being attached by pressure thereto may beattached by pressure to each other with the frame-shaped hydrogenion-conductive film 11 or the gas diffusive film interposed therebetweento produce the electrolyte membrane-electrode assembly. It is therebypossible to obtain the effect of protecting the electrolyte membrane inthe vicinity of the gap between the gasket and the gas diffusionelectrode.

(ii) Embodiment 2

An embodiment of a second production method of the present inventionwill be described by means of FIGS. 4 to 6:

FIG. 4 shows steps from formation of a catalyst layer 22 on a basematerial 21 for an electrolyte membrane to separation and removal of abase material 21a, which is one of two base materials 21a and 21b(semi-assemblies) with the catalyst layer 22 and the electrolytemembrane 23 formed thereon, from an assembly obtained by attachment bypressure of respective electrolyte membranes 23a and 23b of the basematerials 21a and 21b.

First, the catalyst layer 22 is formed on the base material 21 as inFIG. 4(a). The electrolyte membrane 23 is then formed over the area fromthe surface of the catalyst layer 22 to the surface of the base material21 outside the catalyst layer 22, as in FIG. 4(b). In this case, to theformation method of the electrolyte membrane 23 applied may be either amethod of forming it directly on the base material 21 with the catalystlayer 22 formed thereon or a method of transfer-printing the electrolytemembrane produced in advance on the base material for transfer-printingonto the base material 21.

Subsequently, the respective electrolyte membranes 23a and 23b of thetwo base materials 21a and 21b with the catalyst layer 22 and theelectrolyte membrane 23 formed thereon are mutually opposed as in FIG.4(c), which are then attached by pressure and bonded to each other withthe use of a hot pressing machine 24 to obtain a pre-assembly 25. Then,the pre-assembly 25 is irradiated with ultraviolet rays by anultraviolet lamp 26 from one face thereof, as in FIG. 4(d). In each ofthe above steps FIGS. 4(a) to (d), each of the electrolyte membranes 23aand 23b sustains no damage as being supported by the respective basematerials 21a and 21b thereof.

Next, as in FIG. 4(e), the base material 21a is separated from thepre-assembly 25. In this case, a treatment step such as ultravioletirradiation allows elimination of most of the adhesion force between onebase material 21a and the electrolyte membrane 23a, and because theelectrolyte membrane 23a is supported by the base material 21b, it ispossible to separate the base material 21a with ease without causing anydamage to the electrolyte membrane 23a.

FIG. 5 shows steps of separation and removal of one base materials 21afrom the pre-assembly 25 to separation and removal of the other basematerials 21b from the same.

First, as in FIG. 5(a), a pre-assembly 27, from which the base material21a has been separated, is irradiated with ultraviolet rays with anultraviolet lamp 28 from the side of the other base material 21b.Subsequently, the cell members including a gas diffusion layer 29, agasket 30 and a frame-shaped gas diffusive film 31 are piled on the faceon the side where the layer 22a and the electrolyte membrane 23a of theassembly 27 irradiated with ultraviolet rays are exposed, which are thenattached by pressure with a hot pressing machine 32 to be integrated asin FIG. 5(c). In each of the steps FIGS. 5(a) to (c), the electrolytemembranes 23a and 23b sustain no damage as being supported by the basematerial 21b or by the cell members 29 to 31 attached by pressure.

Next, as in FIG. 5(d), the other base material 21b is separated from theintegrated matter as in FIG. 5(c). In this case, adhesion force betweenthe electrolyte membrane 23b and the base material 21b has beendecreased due to the ultraviolet irradiation and, further, theelectrolyte membrane 23b is supported by each of the cell membersattached by pressure so that the base material 21b can be easilyseparated and removed without causing damage to the electrolyte membrane23b. The treatment such as ultraviolet irradiation to decrease adhesionforce between the electrolyte membrane and the base material has thesimilar effect even when conducted after integration of the cell memberswith a pre-assembly 27 irradiated with ultraviolet rays, as in FIG.5(c).

FIG. 6 shows steps for completion of the electrolyte membrane-electrodeassembly in accordance with the present invention. As shown in FIG.6(a), on the face where the catalyst layer 22b and the electrolytemembrane 23b of the assembly (FIG. 5(d)), obtained by integrating theelectrolyte membranes 23a, 23b and the cell members 29 to 31, areexposed, a gasket 33 and a repellent-treated gas diffusion layer 34 arepiled and attached by pressure with a hot pressing machine 35 toconstitute an electrolyte membrane-electrode assembly as in FIG. 6(b).

In the production method in accordance with Embodiment 2 of the presentinvention, as in the production method of Embodiment 1, the essential asthe cell members to be integrated are the gas diffusion layer and thegasket. Further, it is preferable that the frame-shaped gas diffusivefilm or the hydrogen ion-conductive film is integrated.

In the production methods of Embodiments 1 and 2 of the presentinvention, when the electrolyte membrane is transfer-printed to the basematerial, it is necessary to make adhesion force between the basematerial and the electrolyte membrane larger than that between the basematerial for transfer-printing and the electrolyte membrane, or to beable to change adhesion force between the base material and theelectrolyte membrane to be smaller when the electrolyte membrane isformed on the base material, to a degree that the electrolyte membranecan be separated and removed with ease by the treatment step afterformation of the electrolyte membrane.

As for the material for the electrolyte membrane base material which canmake adhesion force to the electrolyte membrane smaller by the treatmentstep by heating, for example, a heat-separating sheet (e.g., “RiverAlpha” No. 3198LS, No. 3198MS, No. 3198HS etc. produced by NITTO DENKOCORPORATION), or the like can be used. This is made by applying aheat-separative adhesive onto a substrate sheet made of polyester. It isfurther effective that a sheet material having formed a layer whichsublimates by heat on the surface of the base material is used. Theexamples of the material which sublimates by heat may include triazole,triazine, benzotriazole, nitrobenzotriazole, methylbenzotriazole,naphthol, quinoline, hydroxyquinoline, quinolisine, morpholine, andcyclohexilamine. By dissolving these materials in a solvent such asalcohol or ether to be applied to the film substrate, it is possible toform a layer which sublimates by heat.

Further, the material for the base material which can make adhesionforce smaller by the treatment step by cooling may be exemplified bynatural rubber, cis-isoprene rubber, styrene/isoprene rubber, butadienerubber, nitrile rubber, chloroprene rubber, chlorosulfonatedpolyethylene, polysulfide rubber, butyl rubber, ethylene/propylenecopolymer, ethylene/propylene/diene terpolymer, urethane rubber,silicone rubber, fluorine rubber and a mixture of these materials. Anadhesion-imparting agent such as an alkylphenol/formadehyde resin, acoumarone/indene resin, a xylene/formadehyde resin or polybutene may beadded to the materials. Moreover, by using a sheet obtained by applyinga mixture of at least one or not less than two of the aforesaidmaterials to a resin film, the similar effect can be obtained.

As for the material for the base material capable of decreasing adhesionforce by the treatment step of irradiating active light rays, forexample, a dicing tape (e.g., “ELEP Holder” UE-111AJ, UE-2092J,NBD-5170K, produced by NITTO DENKO CORPORATION and “Adwill” D-624, D-650and the like, produced by LINTEC CORPORATION, or the like can be used.These are obtained by applying an acrylic adhesive or the like onto asubstrate sheet made of polyolefin, for example. Further, a sheetmaterial having formed a layer, which sublimates by active light rays,on the surface of the base material can be used. The material whichsublimates by irradiation of active light rays may be exemplified by aresist agent such as poly(2,2,2-trifluoroethyl-α-chloroacrylate), and amaterial easy to polymerize with active light rays such as polyacetal.As for active light rays, as well as ultraviolet rays, X-rays,gamma-rays, electron rays or the like can be used.

As for the material for the base material capable of decreasing adhesionforce by the treatment step of bringing the material in contact with asolvent, a sheet material having formed an adherent layer whichdissolves in the solvent on the surface can be used. As for the materialfor the adherent layer, when, for example, the solvent is water,water-soluble ink (e.g., MS-03C produced by JUJO CHEMICAL CO.,LTD.), asynthetic polymer such as polyvinyl alcohol, polyethylene oxide,polyacrylic amid, polyacrylic amine and polyvinyl pyrrolidone, naturalstarch such as potatostarch, tapiocastarch and cornstarch, processedstarch obtained by oxidizing, imparting alpha-structure to,etherificating or esterificating these natural starch, cellulosederivatives such as carboxymethyl cellulose and methyl cellulose, aprotein, gelatin, glue, casein, shellac, gum Arabic, dextrin and thelike can be used. When the solvent is an organic solvent, a naturalrubber, asphalt, a chloroprene-type resin, a nitrile rubber-type resin,a styrene-type resin, butyl rubber, polysulfide, silicone rubber, binylacetate, nitro cellulose or the like can be used.

In the steps of separating the base material from the electrolytemembrane in the production methods in accordance with Embodiments 1 and2 of the present invention, it is also effective to separate the basematerial while spraying a gas to the bonding part of the base materialand the electrolyte membrane. This method causes no damage to theelectrolyte membrane at the time of the separation and further allowsprevention of separation between the electrolyte membrane and thecatalyst layer and between the catalyst layer and the gas diffusionlayer.

As a method for forming the electrolyte membrane on the base material inthe production methods of Embodiments 1 and 2 of the present invention,when a method is taken in which the electrolyte membrane is formed onthe base material for transfer-printing and then the electrolytemembrane is transfer-printed to the base material, it is effective touse as the material for the base material, for example, a porous sheetmade of ultra high molecular weight polyethylene such as “SUNMAP”produced by NITTO DENKO CORPORATION, or a gas permeable porous platemade of paper, synthetic paper, cloth, non-woven fabric, leather,cellulose, cellophane, celluloid or the like. In a case where theelectrolyte membrane is formed directly on the base material, on theother hand, it is not preferable to use the porous base material becausethe solvent of the electrolyte solution infiltrates into the porous basematerial.

It is possible to easily control adhesion force between the basematerial and the electrolyte membrane by depressurizing and pressurizingwith a gas from the face opposite to the face where the electrolytemembrane has been formed by the transfer-printing method on a basematerial made of the gas permeable porous plate, and by changingpressure to be propagated through micro pores of the porous plate to theelectrolyte membrane according to the degree of the depressurization andpressurization. The use of this control method enables separation andremoval of the electrolyte membrane, by depressurization in a step inwhich an increase in adhesion force to the electrolyte membrane isrequired, and by more modest depressurization or pressurization in astep in which the base material is separated.

It is also effective that upon separation of the base material made ofthe porous sheet from the electrolyte membrane, a liquid such as wateris infiltrated into the base material to change adhesion force to theelectrolyte membrane, and then the base material is separated. It ispreferable in this case that the base material itself or the surfacetreatment part of the base material is not invaded by the solvent of theelectrolyte solution.

In the production methods of the Embodiments 1 and 2 of the presentinvention, the base material for transfer-printing is used for carryingthe electrolyte membrane with a thin film thickness andtransfer-printing this to the base material for the electrolytemembrane. As the substrates therefor used can be, for example, a film ofa resin such as polyester, polyfenyl sulfane, polypropylene,polyethylene, polyvinyl chloride, acetate, polystyrene, polycarbonate,polyimide, aramid, polybutylene telephthalate, polyethersulfone,polyether ethylketene, polyetherimide, polysulfone, polyphthalamide,polyamideimide, polyketone or polyalirate, paper, synthetic paper, wovenfabric, non-woven fabric, leather, cellulose, cellophane, celluloid, ametallic plate, a metallic foil or the like. The appropriate thicknessof the base material for transfer-printing is from 10 to 100 μm, and forthe substrate thereof, one with small critical surface tension, namelyone whose adhesion force to the electrolyte membrane is not large ispreferably used in order to make separation properties of theelectrolyte membrane favorable.

For weakening adhesion force to the electrolyte membrane andfacilitating separation of the electrolyte membrane, it is possible touse, for the aforesaid resin film substrate as the base material fortransfer-printing, polyethylene wax, paraffin wax, higher fatty acidalcohol, olganopolysiloxan, anion-type surfactant, cation-typesurfactant, amphoteric surfactant, nonion-type surfactant,fluorochemical surfactant, metallic soap, organic carboxylic acid andthe derivative thereof, a fluorocarbon resin, a silicone-type resin,dimethyl silicone oil, epoxy modified silicone oil, reactive siliconeoil, alkyl modified silicone oil, amino modified silicone oil, areaction compound of a silane coupling agent, an elemental substance ofa lubricant such as silicone rubber, silicone compound or silicone wax,or a mixture of two or more of these.

In the production methods of the Embodiments 1 and 2 of the presentinvention, an electrolyte layer in the electrolyte layer-electrodeassembly is constituted of two electrolyte membranes, and even in thecase of using a thin electrolyte membrane having such a defect as apinhole, the electrolyte layer is formed by attaching by pressure andintegrating the two membranes. There is thereby an extremely lowprobability that the respective defect parts of the membranes areoverlapped to form a through hole, and a highly-reliable PEFC can thusbe obtained.

In this case, it is necessary to form the electrolyte membrane-electrodeassembly such that the air does not remain between the membranes. Thisis of importance for substantially eliminating a channel which bringsabout crossover of the gases between the cathode and anode so as toproduce a reliable PEFC of great power even when the electrolytemembrane with a thin film thickness is used.

When an air layer remains in the bonding part, there is a possibilitythat a proton-conductive channel is cut off, and three parts, the defectpart of the first electrolyte membrane, the air layer and the defectpart of the second electrolyte membrane, form a channel through whichthe fuel gas and the air can path, leading to occurrence of thecrossover.

In order to avoid remanence of the air layer in the bonding part, it isnot necessarily required to completely prevent the air from being caughtin the bonding part upon attachment by pressure, but, after bonding ofthe two membranes, the air remaining in the bonding part may be removedin a vacuum chamber. In this case, it is preferable that the electrolytelayer-electrode assembly is put into the vacuum chamber and then gradualand stepped depressurization is conducted so as to prevent a partialexplosion of the assembly caused by rapid expansion of the remainingair. It is also effective for prevention of the partial explosion thatthe assembly is stood still, while being warmed, in an autoclave atseveral atmospheric pressure before being put into the vacuum chamber.

For preventing the air from getting caught between the membranes uponattachment by pressure, it is also effective to employ a method in whicha solvent such as water or alcohol is sprayed to the bonded face in asmall amount with an atomizer, followed by attachment by pressure.

It is further effective that the two electrolyte membranes are piled andthen attached by pressure in vacuo in the vacuum chamber or in adepressurized atmosphere. The attachment by pressure may also beconducted in an atmosphere of a gas such as hydrogen which passesthrough the membrane with ease for the purpose of facilitating escape ofthe caught air bubbles out of the bonding part. Moreover, as a methodapplicable to the production method of Embodiment 2 of the presentinvention, a preferable method is that two base materials, each havingthe catalyst layer and the electrolyte membrane on one face thereon, arepiled with the respective faces with the electrolyte membrane thereofmutually opposed, and then attached by pressure little by little withrolls from the end like a cleat. A method in which a heat roller is usedfor the attachment by pressure is also effective.

For production of the reliable polymer electrolyte fuel cell of greatpower by the production methods of Embodiments 1 and 2 of the presentinvention, it is effective that the electrolyte membrane is a thinmembrane having a film thickness of 3 to 10 μm.

In the production methods of Embodiments 1 and 2 of the presentinvention, it is preferable that a frame-shaped reinforcing film made ofa hydrogen ion-conductive film or a gas diffusive film is interposedbetween the electrolyte layer and the catalyst layer, between thecatalyst layer and the gas diffusion layer or between the twoelectrolyte membranes forming the electrolyte layer, such that thereinforcing film covers the electrolyte layer in the clearance betweenthe gasket and the gas diffusion electrode.

Thereby, the clearance between the gasket and the gas diffusionelectrode where stress tends to be concentrated most is covered with thereinforcing film, and thus the electrolyte membrane present at theclearance between the gasket and the gas diffusion electrode and in thevicinity thereof are protected, enabling prevention of the electrolytemembrane in this part from being torn or a flaw or of pinhole from beinggenerated. Further prevented in operation of the fuel cell can be thepressure difference between the fuel gas and the air generated betweenthe gasket and the gas diffusion electrode, generation of the pinhole ortorn-membrane due to pressure accompanied by sliding of the membranecaused by changes in moisture, damage to the electrolyte layer such aspartial cut-off with the edge of the gas diffusion electrode, or thelike.

In a case where a hydrogen ion-conductive film is used as thereinforcing film and this film is interposed between the electrolytelayer and the catalyst layer or between the catalyst layer and the gasdiffusion layer, an adhesion property between the catalyst layer and theconductive film becomes favorable. This is due to containment of ahomogenous proton-conductive resin with a hydrogen ion-conductive filmin the catalyst layer. Although the part of the hydrogen-ion conductivefilm to be inserted under the gasket is interposed between the gasketand the electrolyte layer, it should not work against the sealingproperty of the fuel cell because of a favorable adhesion propertybetween the hydrogen ion-conductive film and the gasket. Also in a casewhere this film is arranged between the electrolyte membranes or betweenthe electrolyte layer and the catalyst layer, the arrangement of thefilm does not cause a decrease in reaction area of the gas diffusionelectrode because the film has proton conductivity. As for the hydrogenion-conductive film, a perfluorocarbon sulfonic acid-type electrolytemembrane is particularly preferable as having high intensity. For a filmcorresponding to this film, for example, Nafion 112 produced by Du Pontin the US, Flemion produced by Asahi Glass Co., Ltd., GORE-SELECTproduced by JAPAN GORETEX INC., Aciplex produced by ASAHI KASEICORPORATION or the like can be employed.

Further, when the gas diffusive film is used as the reinforcing film,there is the effect of preventing damage to the electrolyte membrane inthe production process or operation of the fuel cell, as in the case ofusing the hydrogen ion-conductive film. In addition, when the gasdiffusive film is arranged anywhere between electrolyte membranes,between the electrolyte layer and the catalyst layer, and between thecatalyst layer and the gas diffusion layer, there is no decrease inopening ratio of the gas diffusion electrode since proton conductivityin the part covered with the gas diffusive film is not impaired.

As for the gas diffusive film, a film with high gas permeability and athin film thickness and further with sufficient strength is preferablyused, and to a reliable material satisfying these conditions, a filmmade of a fluoropolymer is applied, which may be specificallyexemplified by a porous film made of a tetrafluoro-ethylene resin (e.g.,MICRO-Tex produced by NITTO DENKO CORPORATION), or the like.

Furthermore, in the production methods of Embodiments 1 and 2 of thepresent invention, it is preferable that a frame-shaped thick filmsection is formed in the electrolyte membrane, and the thick filmsection is provided so as to cover the clearance between the gasket andthe gas diffusion electrode.

The thick film section has the function and effect of preventing damageto the electrolyte membrane in the production process or operation ofthe PEFC, as with the aforesaid reinforcing film. Because the thick filmsection is formed of the electrolyte, proton conductivity of the PEFC isvery unlikely to be impaired. As for the method for forming theframe-shaped thick film section on the electrolyte membrane, a method inwhich an electrolyte solution is screen-printed in the shape of frame onan electrolyte membrane formed to have a uniform thickness, a method inwhich the electrolyte solution is spray-applied in the shape of flamewith the use of a metal mask, or the like, is effective.

(2) Second Production Method:

The present invention secondly relates to a production method of anelectrolyte membrane-electrode assembly for a polymer electrolyte fuelcell, the electrolyte membrane-electrode assembly having: a hydrogenion-conductive polymer electrolyte membrane; and a gas diffusionelectrode which contains a catalyst layer and a gas diffusion layer andis bonded to both faces of the hydrogen ion-conductive polymerelectrolyte membrane, the method being characterized by comprising: astep of bonding a hydrogen ion-conductive polymer electrolyte membraneand a catalyst layer via a coating layer; a step of removing the coatinglayer; and a step of obtaining an electrolyte membrane-electrodeassembly by forming a gas diffusion layer on the catalyst layer.

As opposed to the conventional production method of the electrolytemembrane-electrode assembly for the fuel cell, when the polymerelectrolyte membrane is formed directly on the catalyst layer, nopressure should be applied in the process, leading to formation of athin membrane without breakage thereof; however, direct application of apolymer electrolyte raw material solution to the catalyst layer resultsin infiltration of the solution into the porous catalyst layer, and ithas thereby been difficult to obtain a favorable film.

In the present invention, especially for the purpose of enablingformation of a polymer electrolyte membrane having a thin filmthickness, a thin polymer electrolyte membrane is first formed on aspecific medium (e.g., a coating layer), followed by removal of themedium, to eventually obtain a polymer electrolyte membrane-catalystlayer interface. Here, the medium should thus have a relatively smoothsurface, not be porous and be capable of forming a thin polymerelectrolyte membrane.

That is to say, the present invention provides a production method of anelectrolyte membrane-electrode assembly for a polymer electrolyte fuelcell, obtained by bonding the catalyst layer and the gas diffusionelectrode to the both faces of the hydrogen ion-conductive polymerelectrolyte membrane, the method being characterized by comprising: astep (1) of arranging a medium on the catalyst layer; a step (2) offorming a polymer electrolyte membrane on the medium; and a step (3) offorming the assembly by removing the medium.

However, either the step (1) or the step (2) is conducted first. In thefollowing, preferable embodiments of the second production method of thepresent invention will be described in the separate cases of firstconducting the step (1) and of first conducting the step (2).

(iii) Embodiment 3

A production method of an electrolyte membrane-electrode assembly for afuel cell in accordance with Embodiment 3 of the present invention is amethod for first forming a coating layer as a medium on the catalystlayer, the method comprising: a step (a1) of forming a coating layer ona catalyst layer; a step (b1) of applying a hydrogen ion-conductivepolymer electrolyte solution onto the face opposed to the face of thecoating layer in contact with the catalyst layer; a step (c1) ofremoving the coating layer to obtain an electrolyte membrane-catalystlayer assembly; and a step (d1) of forming a gas diffusion layer on thecatalyst layer.

There is a need for eventual removal of the coating layer; in the step(a1), it is effective that the coating layer is formed of a materialwhich sublimates at 200° C. or lower, a material which pyrolyticallydecomposes at 200° C. or lower, a material which decomposes withultraviolet rays and sublimates, a material which decomposes withultraviolet rays and dissolves in a solvent, a water-soluble material,or a material which dissolves in an organic solvent. 200° C. or lower ismentioned here because perfluorocarbon sulfonic acid ionomer as thepolyer electrolyte does not pyrolytically decompose at 200° C. or lower.

The examples of the material which sublimates at 200° C. or lower mayinclude triazole, tiazine, benzotriazole, nitrobenzotriazole,methylbenzotriazole, naphthol, quinoline, hydroxyquinoline, quinolizine,morpholine and cyclohexylamine. The layer can be formed by making apaste of these materials with a solvent such as alcohol or ether, to beapplied.

The examples of the material which pyrolytically decomposes at 200° C.or lower may include polyoxymethylene, poly-α-methylene sulfone,polypropylene oxide, polyisoprene, polymethyl methacrylate andpolymethyl acrylate.

The examples of the material which decomposes with ultraviolet rays andsublimates may include a resist agent such aspoly(2,2,2-trifluoroethyl-α-chloroacrylate) and a material prone todepolymerize with ultraviolet rays such as polyacetal.

The examples of the material which decomposes with ultraviolet rays anddissolves in the solvent may include a photosensitive resin such aspoly(methylisopropenillic ketone).

The water-soluble material may be exemplified by synthetic polymers suchas polyvinyl alcohol, polyethylene oxide, polyacrylic amid, polyacrylicamine and polyvinyl pyrrolidone, natural starch such as potatostarch,tapiocastarch and cornstarch, processed starch obtained by oxidizing,imparting alpha-structure to, etherificating or esterificating thesenatural starch, cellulose derivatives such as carboxymethyl celluloseand methyl cellulose, a protein, gelatin, glue, casein, shellac, gumArabic and dextrin.

The material which dissolves in the organic solvent may be exemplifiedby a natural rubber, asphalt, a chloroprene-type resin, a nitrilerubber-type resin, a styrene-type resin, butyl rubber, polysulfide,silicone rubber, binyl acetate and nitro cellulose.

Next, from the viewpoint that a thin and uniform coating layer can beformed, it is effective that screen printing, a roll coater or a sprayapplication method is used for the formation.

It is possible for the skilled person to select as appropriate themethod for forming the coating layer and the subsequent drying method,according to a material for the coating layer, a condition for theformation, and the like.

Also, for the material for formation of the coating layer, theconcentration thereof and the temperature for the formation may beselected within the range that the membrane can be formed.

Subsequently, in Embodiment 3, the polymer electrolyte membrane isformed on the coating layer formed as thus described, as the step (b1).

Differently from the conventional case where the polymer electrolytemembrane supplied by the rolls is used, it is possible, according tothis method, to form the polymer electrolyte membrane thinner than theconventional one, as thus described.

As for the material for formation of the polymer electrolyte membrane,the same polymer electrolyte solution as the conventional one may beused, and the concentration thereof and the temperature for theformation can be selected as appropriate. Moreover, this polymerelectrolyte layer is effectively formed by the screen printing, the rollcoater or the spray application method, as with the coating layer.

In the step (c1), the coating layer is removed. The way of the removalcan be selected according to a type and characteristic of a materialforming the coating layer, and a method such as heating, ultravioletirradiation, dissolution in water or a solvent can be employed. Althoughit is necessary that the method applied here be carried out under acondition that the performance of the assembly to be obtained is notimpaired, the skilled person can select such a condition as appropriate.

Finally, in the step (d1), the gas diffusion layer is formed on thecatalyst layer by following the conventional method to obtain theelectrolyte membrane-electrode assembly of the present invention. Atthis time, a cell member such as a gasket may be arranged.

(iv) Embodiment 4

Next, a production method in accordance with Embodiment 4 of the presentinvention, which relates to the case of forming the polymer electrolytemembrane on the medium first, is a production method of an electrolytemembrane-electrode assembly obtained by bonding a catalyst layer and agas diffusion layer on both faces of an ion-conductive polymerelectrolyte membrane, the method being characterized by comprising: astep (a2) of forming a hydrogen ion-conductive polymer electrolytemembrane on a polymer film; a step (b2) of arranging a catalyst layer onthe face opposed to the face of the polymer film having the hydrogenion-conductive polymer electrolyte membrane; a step (c2) of removing thepolymer film to obtain an electrolyte membrane-catalyst layer assembly;and a step (d2) of forming a gas diffusion layer on the catalyst layer.

Herein, a polymer film as the medium is formed in advance. For thispolymer film, the material may be the same as that for the coating layerin Embodiment 3 above. Namely, the polymer film can be formed of amaterial which sublimates at 200° C. or lower, a material whichpyrolytically decomposes at 200° C. or lower, a material whichdecomposes with ultraviolet rays and sublimates, a material whichdecomposes with ultraviolet rays and dissolves in a solvent, awater-soluble material, or a material which dissolves in an organicsolvent.

Since the polymer film is formed separately from the gas diffusionlayer, however, it may be formed by, for example, dropping or applyingthe material onto a glass plate, a petri dish or a film, followed bydrying.

The polymer electrolyte membrane is then formed on the polymer film.Also in this case, the same materials as in Embodiment 3 above can beused for the formation by screen printing, the roll coater or the sprayapplication method.

Subsequently, the polymer film with the polymer electrolyte membraneformed on one face thereof is disposed on the catalyst layer of the gasdiffusion electrode by contacting the other face of the polymer filmwithout the polymer electrolyte membrane to the catalyst layer, andfinally the polymer film is removed in the same manner as in the case ofremoving the coating layer in Embodiment 3 above so that the assembly inaccordance with the present invention can be obtained. There is noparticular limitation to the method for disposal of the polymer film onthe gas diffusion electrode, and it may be mechanically disposed, forexample.

(v) Embodiment 5

Furthermore, the present invention relates to a production method of anelectrolyte membrane-electrode assembly obtained by bonding a catalystlayer and a gas diffusion electrode to both faces of an ion-conductivepolymer electrolyte membrane, the method being characterized bycomprising: a step (a3) of forming a coating layer composed of ahydrogen ion-conductive polymer electrolyte on a catalyst layer; a step(b3) of applying a hydrogen ion-conductive polymer electrolyte solutiononto the face opposite to the face of the coating layer in contact withthe catalyst layer; a step (c3) of removing the coating layer to obtainan electrolyte membrane-catalyst layer assembly; and a step (d3) offorming a gas diffusion layer on the catalyst layer.

In Embodiment 5, the material for the coating layer is the same as thatfor the polymer electrolyte membrane. As thus described, the medium isrequired for preventing infiltration of the polymer electrolyte solutioninto the catalyst layer; in this embodiment, the gelation phenomenon ofthe polymer electrolyte is utilized and the gelated layer is used as alayer for preventing the infiltration into the catalyst layer.

That is to say, first, a small amount of a polymer electrolyte membraneraw material solution is sprayed with a spray to the catalyst layer toevaporate the solvent. Because the polymer electrolyte solution isgelated when a solvent such as ethyl alcohol is used and theconcentration of the polymer electrolyte becomes from 10 to 20%, ajelly-like or half-solid gelated layer is formed simultaneously withevaporation of the solvent.

Since appropriate selections of a distance between the spray and thecatalyst layer, a spraying condition, and a spraying amount enablecontrol on the evaporation state of the solvent of the polymerelectrolyte solution upon arrival thereof at the surface of the catalystlayer, it is possible to limit infiltration of the solution into thecatalyst layer to just the surface part thereof. Repetition of thisoperation several times allows the polymer electrolyte solution to formthe thin, gelated layer so as to totally cover the surface of thecatalyst layer. Thereafter, this catalyst layer is dried at 100 to 140°C. for a short time to form a coating layer which no longer dissolves ina solvent such as ethyl alcohol. Next, when the raw material solution ofthe polymer electrolyte membrane is applied onto the coating layer, thecoating layer becomes a layer for interrupting the raw material solutionto the catalyst layer, resulting in favorable formation of the polymerelectrolyte membrane. Because the material for the coating layer is thesame as that for the polymer electrolyte membrane, the coating layer canexert proton conductivity as a part of the polymer electrolyte membraneafter formation of the polymer electrolyte membrane.

It should be noted that in the method thus described, although thepolymer electrolyte membrane in the state that one face thereof is incontact with the gas diffusion layer is formed, with the thin polymerelectrolyte membrane having been formed, the catalyst layer and thecarbon paper can be bonded to the other face of the polymer electrolytemembrane to obtain the electrolyte membrane-electrode assembly for thefuel cell.

(vi) About the Catalyst Layer

The present inventors have found that an excellent electrolytemembrane-electrode assembly for a fuel cell can be produced by forming acatalyst layer with a mixture containing a catalyst body composed of anoble metal catalyst and a carbon powder, a polymer electrolyte, and apolyfunctional basic compound.

Accordingly, the present invention provides an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell,comprising a polymer electrolyte membrane and a pair of electrodesarranged on both sides of the polymer electrolyte membrane, and beingcharacterized in that at least one of the electrodes is constituted of agas diffusion layer and a catalyst layer composed of: a mixturecontaining a catalyst body composed of a noble catalyst and a carbonpowder, a polymer electrolyte, and a polyfunctional basic compound.

In this assembly, it is effective that the polyfunctional basic compoundis polyfunctional amine.

It is also effective that the catalyst layer contains from 0.1 to 10 wt% of polyfunctional basic compound with respect to the polymerelectrolyte.

The present invention further provides an electrolyte membrane-electrodeassembly for a polymer electrolyte fuel cell, comprising a polymerelectrolyte membrane and a pair of electrodes arranged on both sides ofthe polymer electrolyte membrane, and being characterized in that atleast one of the electrodes is constituted of a gas diffusion layer anda catalyst layer composed of: a catalyst body composed of a noblecatalyst and a carbon powder having a basic surface functional group;and a polymer electrolyte.

Also in this assembly, it is effective that the basic surface functionalgroup is amine.

The present invention further provides an electrolyte membrane-electrodeassembly for a polymer electrolyte fuel cell, comprising a polymerelectrolyte membrane and a pair of electrodes arranged on both sides ofthe polymer electrolyte membrane, and being characterized in that thepolymer electrolyte membrane includes a polyfunctional basic compound,and the assembly comprises the polymer electrolyte membrane and a gasdiffusion electrode.

Also in this case, it is effective that the polyfunctional basiccompound is polyfunctional amine. Further, it is effective that thepolymer electrolyte membrane contains a polyfunctional basic compound at1 to 10 wt % of the polymer electrolyte. It is also effective that themain chain part of the polyfunctional basic compound is perfluoronated.

The assembly for the polymer electrolyte fuel cell composed of thepolymer electrolyte membrane and the gas diffusion electrode inaccordance with the present invention includes a polyfunctional basiccompound or a carbon powder having a basic surface functional group.

This polyfunctional basic compound can be contained in the polymerelectrolyte membrane and/or the catalyst layer constituting the assemblyand is bonded to a part of the sulfonic acid group of ionomer as thepolymer electrolyte to form a three-dimensional network so that theionomer becomes resistant to flowing into the gas diffusion layer withdrained water.

The carbon powder having the basic surface functional group can becontained in the catalyst layer constituting the electrolytemembrane-electrode assembly and is bonded to a part of the sulfonic acidof ionomer as the polymer electrolyte to prevent the ionomer frommelting into drained water and flowing out. Thereby, the gas diffusionlayer maintains gas permeability, and the catalyst layer and the polymerelectrolyte membrane exert the function of being resistant to impairingproton conductivity.

An electrolyte membrane-electrode assembly composed of a polymerelectrolyte and a pair of electrodes arranged on both sides of thepolymer electrolyte membrane will be described:

When the polyfunctional basic compound is contained in the catalystlayer, the electrolyte membrane-electrode assembly for the polymerelectrolyte fuel cell of the present invention is composed of a polymerelectrolyte membrane and a pair of electrodes arranged on both faces ofthe polymer electrolyte membrane, and at least one of the electrodes isconstituted of: a catalyst layer composed of a mixture containing acatalyst body composed of a noble metal catalyst and a carbon powder, apolymer electrolyte, and a polyfunctional basic compound; and a gasdiffusion layer made of carbon paper, carbon cloth or the like.

As FIG. 12 shows, this polyfunctional basic compound 211 is bonded to apart of the sulfonic group of ionomer 212 to form a three dimensionalnetwork, exerting the effect of inhibiting flowing out of the ionomer.

As for the polyfunctional basic compound, one having, in one molecule,two or more of functional groups capable of reacting with the sulfonicgroup may be employed. The examples may include difunctional amine suchas ethylene diamine, 1,2-propylene diamine, tetramethylene diamine,hexamethylene diamine, heptamethylene diamine, octamethylene diamine andnonamethylene diamine, trifunctional amine such as diethylene triamine,aromatic polyfunctional amine such as benzene diamine, 1,2,3-triaminobenzene and 1,2,3,4-tetraamino benzene, compounds having amidino groupssuch as 1,5-diazabicyclo[4.3.0]nona-5-ene and1,8-diazabicyclo[5.4.0]undeca-7-ene, polysaccharide including N such asstreptomycin, vitamins such as vitamin B2 and vitamin B12,azanaphtalenes such as xanthan pterin, leuco pterin and methotrexate,alkaloids such as kinin, strychnine and brucine, polypeptide such asglycyl alanine, alanyl glycine, aspartame and glutathione, pyridazine,pyrimidine, triazines, tetrazines, cinnoline, quinazoline, phtalazine,quinozaline, pteridine, lysergic acid diethylamide, adenine,benzoimidazole, purine, hydrazide, nicotine, tetrahydrofolic acid,hexamethylenetetramine, and 4,4′-diaminobiphenyl.

Among them, polyfunctional amine is preferable from the viewpoint ofoccurrence of a chemical reaction of an acid with a base in a relativelymild condition.

It is also preferable that hydrogen in the skeleton part of thepolyfunctional basic compound is perfluoronated. This is because, withhydrogen perfluoronated, decomposition attributed to a reaction ofdrawing out hydrogen atoms, or the like, can be prevented, and highreliability can thus be realized.

The perfluoronated polyfunctional amine may be exemplified bytetrafluoro-p-phenylenediamine, 4,4′-diamonooctafluorobiphenyl, and2,4,6-tris(perfluorohepthyl)-1,3,5-triazine.

It is preferable that the polyfunctional basic compound in the catalystlayer is from 0.1 to 10 wt % with respect to the polymer electrolyte.This is because, when a replacement ratio is about several % of thetotal number of the acidic groups such as the sulfonic group, there is asmall influence on proton conductivity.

Next, in a case where the catalyst layer contains the carbon powderhaving the basic surface functional group, an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with the present invention comprises a polymer electrolytemembrane and a pair of electrodes arranged on both sides of the polymerelectrolyte membrane, and at least one of the electrodes is constitutedof a gas diffusion layer and a catalyst layer composed of: a catalystbody composed of a noble metal catalyst and a carbon powder having abasic surface functional group; and a polymer electrolyte.

As FIG. 13 shows, the basic surface functional group 221 of the carbonpowder 223 in the catalyst layer is bonded to a part of the sulfonicacid group of ionomer 224, exerting the effect of suppressing flowingout of the ionomer. The basic surface functional group 221 on the carbonpowder 223 is replaced by, for example, a carboxyl group present on thesurface of the carbon powder, or the like, before mixture with theionomer. As for the basic surface functional group, amines arepreferable from the viewpoint of occurrence of a chemical reaction of anacid with a base in a relatively mild condition.

The number of the basic surface functional groups on the carbon powdermay be one. In a case where the basic material is a monomolecule, thebasic material flows away with the ionomer since there is nocrosslinking effect without two or more of the functional groups. In acase where the substrate of the basic material is the carbon powder, onthe other hand, since the carbon powder is fixed in the catalyst layer,the basic functional group will not flow away with the ionomer even whenthe number thereof is one. In view of the aforesaid functions, there isno need for presence of the basic functional group on the surface of allthe carbon powders. There is also no need for bonding of all the ionomerto the surface functional group. These are because bonding to a part ofthe ionomer allows sufficient suppression of the flowing out due to ananchor effect.

Further, when the polyfunctional basic compound is included in thepolymer electrolyte membrane, an electrolyte membrane-electrode assemblyfor a polymer electrolyte fuel cell in accordance with the presentinvention is an assembly composed of a polymer electrolyte membrane andelectrodes arranged on both faces of this membrane, and the polymerelectrolyte membrane includes the polyfunctional basic compound.

As thus described, it is also preferable here that the polyfunctionalbasic compound is polyfunctional amine and that the weight of thepolyfunctional basic compound with respect to the polymer electrolyte isfrom 1 to 10 wt %. This is because a low replacement ratio of the acidicgroup such as the sulfonic acid results in a small influence on protonconductivity.

Below, the present invention will be described more specifically by theuse of examples; however the present invention is not limited to these:

EXAMPLE 1

An electrolyte membrane-electrode assembly was produced by the stepsabove described by means of FIGS. 1 to 3, and then a PEFC was fabricatedusing this assembly.

First, by the steps FIGS. 1(a) to (e), an electrolyte membrane 2 wasformed on a base material 3 by a transfer-printing method, and acatalyst layer 6 was formed thereon by the transfer-printing method.

An electrolyte solution was prepared by adding ethyl alcohol to analcohol solution (Brand name: Flemion FSS-1 solution, produced by AsahiGlass Co., Ltd.) containing 9 wt % of an electrolyte, for preventinggelation, to be diluted to be an 8 wt % solution. A polypropylene film(Brand name: Torayfan, produced by Toray Industries, Inc.) with a filmthickness of 50 μm was used for a base material 1 for transfer-printing.An application film of the electrolyte solution was heated and driedwith an infrared ray heater to produce an electrolyte membrane 2 with afilm thickness of 6 μm. An ultraviolet separation tape (D-624, producedby LINTEC CORPORATION) was used for the base material 3 for theelectrolyte membrane.

A polypropylene film (Brand name: Torayfan, produced by TorayIndustries, Inc.) with a film thickness of 50 μm was used for a basematerial 5 for a catalyst, on which a catalyst layer 6 was formed in thefollowing manner: First, 40 g of product obtained by making conductivecarbon particle (Brand name: ketjen black EC, produced by KetjenblackInternational Corporation) with a specific surface area of 800 m²/g,carrying a platinum particle with a mean particle size of about 30angstrom thereon in the weight ratio of 1:1, was put into a glasscontainer. 120 Gram of water was added into this glass container whilebeing stirred with a ultrasonic sound stirrer, and then 210 g of FlemionFSS-1 solution was added thereinto while being stirred, to prepare acatalyst paste. This paste was stirred with the ultrasonic sound stirrerfor one hour, and then developed on the base material 5 for the catalystusing a barcoater, followed by drying at room temperature, to form acatalyst layer 6. In the step of attaching by pressure the catalystlayer 6 to the electrolyte membrane 2, the temperature was raised to100° C. while they were pressurized at 4 kgf/cm², and then they were hotpressed at 40 kgf/cm².

Next, a semi-assembly of the electrolyte memebrane-electrode wasconstituted by the steps FIGS. 2(a) to (d). In the step of ultravioletirradiation, ultraviolet rays of 365 nm and 2000 mJ/cm² were irradiated.Carbon paper with a size of 100 mm×200 mm, repellent treated by beingsoaked in a solution obtained by diluting with water an aqueousdispersion (D1, produced by DAIKIN INDUSTRIES, LTD.) containing 50 wt %of fluorocarbon resin, to make the concentration a half, was used as agas diffusion layer 10; a hydrogen ion-conductive film reinforced with afluorocarbon polymer cloth was used as a hydrogen ion-conductive film11.

Subsequently, an electrolyte membrane-electrode assembly was constitutedby the steps FIGS. 3(a) to (c). In each of the steps of hot pressing inFIG. 2 and FIG. 3, after the temperature was raised to 130° C.simultaneously with pressurization at 5 kgf/cm², the hot pressing wasconducted at 50 kgf/cm² for 10 minutes.

After the hot pressing in FIG. 3, for the purpose of removing the airout of the spaces between the electrolyte membranes of the attached bypressure electrolyte membrane-electrode assembly, the electrolytemembrane-electrode assembly was put into a depressurized container, inwhich there was conducted slow depressurization from atmosphericpressure to 0.1 atm in ten minutes. Thereafter conducted was furtherdepressurization down to 0.01 atm in 10 minutes and, then, to 0.001 atm,and the assembly was stood still for 30 minutes. This electrolytemembrane-electrode assembly was then taken out of the depressurizedcontainer for observation and it was confirmed, as a result, that theair having been caught between the electrolyte membranes was removed inthe depressurized container and air bubbles disappeared.

Next, a PEFC was fabricated using this electrolyte membrane-electrodeassembly to evaluate the actuation characteristic thereof. First,respective manifold apertures for circulation of the fuel gas and theoxidant gas were formed in a gasket 9 in the electrolytemembrane-electrode assembly. A separator with an oxidant gas flowchannel formed was placed on one face of the electrolytemembrane-electrode assembly, and a separator with a fuel gas flowchannel formed was placed on the other face of the assembly, to obtain aunit cell. Two of the unit cells were stacked, the stack of the two unitcells was interposed between separators with a cooling medium flowchannel formed, and by repetition of this pattern, a fuel cell stackincluding 100 unit cells was fabricated. Each of the separators was madeto have a thickness of 1.3 mm, and the oxidant gas flow channel, thefuel gas flow channel or the cooling medium flow channel was made tohave a depth of 0.5 mm. A current correcting plate, an insulating plateand an end plate were disposed at each of both ends of the fuel cellstack, which were fixed with a fastening rod to fabricate a PEFC. Thefastening pressure at this time was made 10 kgf/cm².

The PEFC as thus fabricated was subjected to a successive powergeneration test in such conditions as a fuel utilization ratio of 85%,an oxygen utilization ratio of 60%, a current density of 0.7 A/cm² toobtain a discharge voltage of 0.7 V per a unit cell. Therefrom, highoutput of 0.49 W/cm² was obtained. In this test, the concentration ofcarbon monoxide of a gas obtained by steam-reforming methane wasdecreased to be 50 ppm or lower and the gas was humidified and heated tohave a dew point of 70° C., and then supplied to the fuel cell electrode(anode) side as a fuel gas, while the air humidified and heated to havea dew point of 45° C. was supplied to the air electrode (cathode) sideas an oxidant gas. The temperature of the PEFC was kept at 75° C. byusing cooling water as the cooling medium.

EXAMPLE 2

The same electrolyte solution as that in Example 1 was applied onto thesame base material for the electrolyte membrane as that in Example 1with the use of a coater, which was heated and dried with an infraredray heater to form the electrolyte membrane 2 with a film thickness of 6μm directly on the base material. Except the above, an electrolytemembrane-electrode assembly and a PEFC were produced in the same manneras in Example 1, to be evaluated.

As a result of the depressurization test on the electrolytemembrane-electrode assembly, it was confirmed that the air having beencaught between the electrolyte membranes was removed in thedepressurized container and air bubbles disappeared. Further, in thesuccessive power generation test on the PEFC using this electrolytemembrane-electrode assembly, a high discharge voltage of about 0.7 V pera unit cell was obtained, as in Example 1.

COMPARATIVE EXAMPLE 1

Except that a fluorine polymer film (Nephron tape, produced by NICHIASCorporation) with a thickness of 50 μm as a material for the reinforcingfilm was used in place of the hydrogen ion-conductive film in Example 1,an electrolyte membrane-electrode assembly and a PEFC were produced andevaluated in exactly the same manner as in Example 1. As a result of thedepressurization test, it was confirmed that the bonding part of thereinforcing film of the assembly taken out of the depressurizedcontainer had become easy to be pealed off. In the successive powergeneration test on the PEFC using this electrolyte membrane-electrodeassembly, although a discharge voltage of about 0.7 V per a unit cellwas obtained as in Example 1, the effective reaction area of theelectrode decreases by about 2%, thus lowering output accordingly.

EXAMPLE 3

FIG. 7 schematically shows a production process of the electrolytemembrane-electrode assembly in accordance with the present example.

First, for obtaining a catalyst layer 103, a carbon powder carrying from10 to 30 wt % of a platinum catalyst thereon was mixed with N-butylacetate such that the weight ratio of above platinum and N-butyl acetatewas 1:120, to obtain a dispersion of the platinum catalyst. While thedispersion was stirred with a magnetic stirrer, an ethyl alcoholsolution of the polymer electrolyte was added dropwise until the amountratio of the platinum and the polymer electrolyte became 1:2, which wasthen made to give a paste with the use of an ultrasonic dispersionmachine. As for the ethyl alcohol solution of the polymer electrolyte,the Flemion FSS-1 solution produced by Asahi Glass Co., Ltd. was used.

This catalyst paste was applied onto one face of carbon paper as a basematerial 104 produced by Toray Industries, Inc. with a size of 100mm×200 mm, on which from 20 to 60 wt % of atetrafluoroethylene-hexafluoropropylene copolymer was welded in advance,and then dried at 50 to 60° C. to obtain a gas diffusion electrode. Acatalyst layer 103 as thus formed had a thickness of 30 to 40 μm.

Next, an aqueous solution of hydroxypropyl methylcellulose (60SH4000produced by Shin-Etsu Chemical Co., Ltd.) with a concentration of 3% ofand viscosity of 4000 CPS was applied by the roll coater method,followed by drying, to form a coating layer 102.

Subsequently, the Flemion FSS-1 solution with the viscosity thereofadjusted, as the polymer electrolyte solution, was applied to thecatalyst layer side of the gas diffusion layer with the coating layerformed, and then ethyl alcohol as the solvent was removed with a dryer,to obtain a gas diffusion electrode as in FIG. 7(c).

It was then baked with the dryer in the condition of 200° C. for 30minutes. This baking step allowed elimination of the coating layer 102having been formed on the catalyst layer 103, resulting in obtainment ofa gas diffusion electrode where the polymer electrolyte membrane 101 wasin contact with the surface of the catalyst layer 103, as shown in FIG.7(d). The polymer electrolyte membrane 101 at this time had a thicknessof 5 to 20 μm, and hence a polymer electrolyte membrane layer with auniform film thickness which was not immersed into the catalyst layerwas obtained.

The gas diffusion electrode with the polymer electrolyte layer having athickness of 12 μm as thus produced and the gas diffusion electrode withonly the catalyst layer formed were laminated such that the respectivecatalyst layers thereof were inwardly opposed to each other, thetemperature was raised to 150° C. simultaneously with pressurization at5 kgf/cm² with the use of a hot pressing machine and, after thetemperature was raised to 150° C., hot pressing was conducted at 50kgf/cm² for 10 minutes.

Using this assembly, a voltage was measured at 0.7 A/cm² when a celltemperature was 75° C., a negative electrode bubbler temperature was 70°C., a positive electrode bubbler temperature was 65° C., a hydrogenutilization ratio was 70% and an air utilization ratio was 40%, to be0.70 V. Namely, the output power was 0.49 W/cm², and such high outputpower could be obtained.

It should be noted that, although the example of using carbon paper asthe base material 104 was described in the present example, the basematerial 104 is not necessarily required to be carbon paper, but it maybe a sheet of a polymer such as polypropylene (PP) or polyethyleneterephthalate (PET). When the base material 104 is such a sheet, carbonpaper may be bonded after separation.

COMPARATIVE EXAMPLE 2

FIG. 10 schematically shows a production process of an electrolytemembrane-electrode assembly in accordance with the present comparativeexample.

The same method as that in Example 3 was conducted until formation ofcatalyst layers 143 and 145, on gas diffusion layers 142 and 144, toobtain gas diffusion electrodes 146 and 147.

Subsequently, Flemion SH50 (thickness: 50 μm) 141, produced by AsahiGlass Co., Ltd. as the polymer electrolyte membrane was interposedbetween the gas diffusion electrodes 146 and 147 with the catalystlayers 143 and 145 inwardly opposed to each other, the temperature wasraised to 150° C. simultaneously with pressurization at 5 kgf/cm² withthe use of a hot pressing machine and, after the temperature was raisedto 150° C., hot pressing was conducted at 50 kgf/cm².

Using this assembly, a voltage was measured at 75° C. and at 0.7 A/cm²in the same manner as Example 3, to be 0.55 V. Namely, the obtainedoutput power was 0.385 W/cm², which was lower compared to Example 3.This is due to the internal resistance of the polymer electrolytemembrane; in a membrane with a large film thickness, a large decrease involtage occurs.

COMPARATIVE EXAMPLE 3

In the present comparative example, the polymer electrolyte solution wasapplied directly onto the catalyst layer 103 by the roll coater method.Other conditions were made the same as Example 3 and a gas diffusionelectrode was produced.

In the gas diffusion electrode as thus produced, the polymer electrolytesolution was infiltrated into the porous parts of the catalyst layer 103at the time of the application and a boundary line 108 of theinfiltrated polymer electrolyte solution appeared, as shown in FIG. 11.This led to generation of numerous small concavities and convexities onthe surface of the polymer electrolyte membrane, and thus the thicknessof the membrane was not uniform, with which the gas diffusiveness of thecatalyst layer 103 did not function, and hence it could not be used asthe electrode.

EXAMPLE 4

FIG. 8 schematically shows a production process of an electrolytemembrane-electrode assembly for a fuel cell in accordance with thepresent invention.

First, a gas diffusion electrode with the catalyst layer 103 wasobtained in the same manner as in Example 3. Next, an aqueous solutionwith a concentration of 1% of hydroxypropyl methylcellulose (60SH4000produced by Shin-Etsu Chemical Co., Ltd.) was dropped onto a glass plateto be developed by the casting method, followed by drying, to obtain afilm 122.

After the Flemion FSS-1 solution as the polymer electrolyte was appliedonto the film 122 by the roll coater method, an ethyl alcohol componentwas removed to obtain a film with the polymer electrolyte layer as inFIG. 8(a). At this time, the polymer electrolyte layer had a thicknessof 12 μm.

Next, as shown in FIG. 8(b), this film with the polymer electrolytelayer was laminated with the above-produced gas diffusion electrode withthe catalyst layer 103 and baked with the dryer in the condition of 200°C. for 30 minutes. This baking step allowed elimination of the film 122,resulting in obtainment of a gas diffusion electrode where the polymerelectrolyte membrane 101 was in contact with the catalyst layer 103, asshown in FIG. 8(c).

The gas diffusion electrode with the polymer electrolyte layer as thusproduced and the gas diffusion electrode with only the catalyst layer103 were laminated such that the respective catalyst layer thereof suchthat the layers were inwardly opposed to each other as in Example 3, thetemperature was raised to 150° C. simultaneously with the pressurizationat 5 kgf/cm² with the use of a hot pressing machine and, after thetemperature was raised to 150° C., hot pressing was conducted at 50kgf/cm².

Using this assembly, a voltage was measured at 75° C. and at 0.7 A/cm²,to be 0.69 V. Namely, the obtained output power was 0.48 W/cm², whichwas as high out put as that in Example 3.

EXAMPLE 5

FIG. 9 schematically shows a production process of an electrolytemembrane-electrode assembly for a fuel cell in accordance with thepresent example.

First, a gas diffusion electrode with the catalyst layer 103 wasproduced in the same manner as in Example 3. Then, this gas diffusionelectrode with the catalyst layer was arranged onto a hot plate at 50°C. and an ethyl alcohol solution with 8 wt % of Flemion FSS-1 (a polymerelectrolyte) was spray-applied with a spray nozzle 105 onto the catalystlayer of the gas diffusion electrode. First, 5 cc of Flemion FSS-1solution was sprayed to the catalyst layer of the gas diffusionelectrode at a distance of 80 cm or longer, ethyl alcohol as the solventwas evaporated with the solution on just the fall, resulting information by precipitation of a gelated layer on the surface of thecatalyst layer. Next, 5 cc of Flemion FSS-1 solution was further sprayeduniformly to the gelated layer. After repetition of this operation threetimes, the gas diffusion electrode was stood still on the hot plate at100° C. for 10 minutes to harden the gel as the polymer electrolyte,thereby forming a thin layer 131 of the polymer electrolyte. Thereafter,the Flemion FSS-1 solution was applied onto the thin layer 131 with theroll coater. Subsequently, the gas diffusion electrode with the polymerelectrolyte membrane formed was dried at 150° C. for 60 minutes toobtain the gas diffusion electrode with the polymer electrolytemembrane, as in FIG. 9(c). The polymer electrolyte layer at this timehad a thickness of 12 μm.

The gas diffusion electrode with the polymer electrolyte layer as thusproduced and the gas diffusion electrode with only the catalyst layer103 were laminated such that the respective catalyst layers wereinwardly opposed to each other and, while pressurization at 5 kgf/cm²was conducted with the use of the hot pressing machine, the temperaturewas raised to 150° C., followed by hot pressing at 50 kgf/cm² after thetemperature raise to 150° C.

Using this assembly, a voltage was measured at 0.7 A/cm² and at 75° C.,to be 0.71 V. Namely, the obtained output power was 0.50 W/cm², whichwas as high out put as that in Example 3.

Although the roll coater method was employed in the present example, thesimilarly uniform coating layer and polymer electrolyte layer can beproduced by the screen printing method.

REFERENCE EXAMPLE 1

First, 6.0 g of carbon fine powder carrying 25 wt % of platinum catalystthereon was added to 50.0 g of n-butyl acetate (CH₃COOCH₂(CH₂)₂CH₃),which was stirred for 10 minutes with the use of a stirrer while beingsubjected to ultrasonic sound, to be dispersed. Next, the dispersion wasadded step by step with 40.0 g of ethanol solution with 9 wt % of apolymer electrolyte (Flemion produced by Asahi Glass Co., Ltd.), whilebeing stirred, so that colloid of the polymer electrolyte was attachedonto the surface of the carbon fine powder carrying the catalystthereon. When the stirring was stopped one hour after addition of theentire polymer electrolyte solution, a clear supernatant liquid changedto be transparent. Subsequently, this mixed solution with the catalystwas mixed with 0.10 g of hexamethylene diamine, and ultrasonic soundlydispersed for one hour, to obtain a catalyst paste.

Next, it was soaked in a fluorocarbon resin dispersion (ND-1 produced byDAIKIN INDUSTRIES, LTD.), and then about 30 μm of the catalyst paste wasapplied onto a carbon paper substrate produced by Toray Industries, Inc.having been baked at 300° C.

Further, on both faces of a polymer electrolyte membrane having a filmthickness of 50 μm (Flemion SH50 produced by Asahi Glass Co., Ltd.), theelectrodes were hot pressed for 10 minutes at a temperature of 120 to140° C. by applying pressure of 50 to 70 kg/cm² to produce anelectrolyte membrane-electrode assembly.

This electrolyte membrane-electrode assembly was interposed betweenseparators to assemble a unit cell, which was operated for 250 hours insuch a condition as a cell temperature of 75° C., a hydrogen dew pointof 70° C., an air dew point of 65° C., a hydrogen utilization ratio of70%, an oxygen utilization ratio of 40% and a current density of 0.7A/cm²; the voltage decreased by 0.03 V from the initial voltage of 0.65V.

REFERENCE EXAMPLE 2

6.0 Gram of a carbon fine powder carrying 25 wt % of platinum catalystthereon was added to 50.0 g of n-butyl acetate (CH₃COOCH₂(CH₂)₂CH₃),which was stirred for 10 minutes with the use of a stirrer while beingsubjected to ultrasonic sound, to be dispersed. Next, the dispersion wasadded step by step with 40.0 g of ethanol solution with 9 wt % of apolymer electrolyte (Flemion produced by Asahi Glass Co., Ltd.), whilebeing stirred, so that colloid as the polymer electrolyte was attachedonto the surface of the carbon fine powder carrying the catalystthereon. After adding the entire polymer electrolyte solution, thestirring was further continued for one hour, to obtain a catalyst paste.

It was soaked into a fluorocarbon resin dispersion (ND-1 produced byDAIKIN INDUSTRIES, LTD.), and then about 30 μm of the catalyst paste wasapplied onto a carbon paper substrate produced by Toray Industries, Inc.having been baked at 300° C.

Further, on both faces of a polymer electrolyte membrane having a filmthickness of 50 gm (Flemion SH50 produced by Asahi Glass Co., Ltd.), theelectrodes were hot pressed for 10 minutes at a temperature of 120 to140° C. by applying pressure of 50 to 70 kg/cm² to produce anelectrolyte membrane-electrode assembly.

This cell was operated for 250 hours in the same condition as inReference Example 1, to observe a voltage decrease by 0.12 V from theinitial voltage of 0.67 V.

REFERENCE EXAMPLE 3

First, 7.0 g of carbon fine powder carrying 25 wt % of platinum catalystthereon, 20 ml of ethanol, 1.0 g of hyxamethylene diamine were put intoa three-necked flask and reflex for 10 minutes. This dispersion wasfiltrated, which was then sufficiently washed with ethanol and waterthrough filter paper, followed by drying, to obtain a carbon fine powdercarrying the platinum catalyst thereon with a part of the carboxylgroups on the surface amino-bonded to hyxamethylene diamine.

6.0 Gram of this carbon fine powder carrying the platinum catalystthereon was added to 50.0 g of n-butyl acetate (CH₃COOCH₂(CH₂)₂CH₃),which was stirred for 10 minutes with the use of a stirrer while beingsubjected to ultrasonic sound, to be dispersed. Next, the dispersion wasadded step by step with 40.0 g of ethanol solution with 9 wt % of apolymer electrolyte (Flemion produced by Asahi Glass Co., Ltd.), whilebeing stirred, so that colloid of the polymer electrolyte was attachedonto the surface of the carbon fine powder carrying the catalystthereon. After adding the entire polymer electrolyte solution, thestirring was further continued for one hour to obtain a catalyst paste.

Subsequently, in the same manner as in Reference Example 1, after it wassoaked in a fluorocarbon resin dispersion (ND-1 produced by DAIKININDUSTRIES, LTD.), about 30 μm of the catalyst paste was applied onto acarbon paper substrate produced by Toray Industries, Inc. having beenbaked at 300° C.

Further, on both faces of a polymer electrolyte membrane having a filmthickness of 50 μm (Flemion SH50 produced by Asahi Glass Co., Ltd.), theelectrodes were hot pressed for 10 minutes at a temperature of 120 to140° C. by applying pressure of 50 to 70 kg/cm² to produce anelectrolyte membrane-electrode assembly.

This electrolyte membrane-electrode assembly was interposed betweenseparators to obtain a unit cell, which was operated for 250 hours inthe same condition as in Reference Example 1, to observe a voltagedecrease by 0.04 from the initial voltage of 0.66 V.

REFERENCE EXAMPLE 4

0.05 Gram of hyxamethylene diamine was mixed into 40 ml of ethanolsolution with 7 wt % of a polymer electrolyte (Flemion produced by AsahiGlass Co., Ltd.) and stirred with ultrasonic sound, which were put intoa petri dish with a diameter of 12 cm and dried at room temperature allthe day, followed by drying at 130° C. for two hours, to obtain apolymer electrolyte cast membrane with a thickness of 50 μm. This wasinterposed by carbon paper with a catalyst layer produced in exactly thesame manner as in Comparative Example 1 to produce an electrolytemembrane-electrolyte assembly, thereby obtaining a unit cell.

This electrolyte membrane-electrode assembly was interposed betweenseparators to assemble a unit cell, which was operated for 250 hours inthe same condition as in Reference Example 1, to observe a voltagedecrease by 0.05 from the initial voltage of 0.63 V.

It is to be noted that, although the catalyst paste was applied onto thecarbon paper substrate to produce the gas diffusion electrode inReference Examples 1 to 4 above, because the present invention ischaracterized in the compositions of the catalyst layer and/or thepolymer electrolyte membrane, it goes without saying that the similareffect can exert in other production methods such as a method in which acatalyst paste obtained by dispersing a carbon fine powder carryingplatinum thereon and a polymer electrolyte in ethanol is applied to afilm made of polypropylene, Teflon or the like one time, which is thenthermally transfer-printed onto a polymer electrolyte membrane toproduce an electrolyte membrane-electrode assembly, and a method inwhich the catalyst paste is applied directly onto the polymerelectrolyte membrane.

According to the present invention, a highly effective and reliablepolymer electrolyte fuel cell of great power with low internalresistance can be obtained. Moreover, according to the presentinvention, an electrolyte membrane-electrode assembly, which is capableof using perfluorocarbon sulfonic acid ionomer with high protonconductivity and of excellent performance, has low internal resistanceand is suitable for a low humidifying or no humidifying activationbecause an electrolyte membrane with a thin film thickness can be formedon a catalyst layer, and a PEFC can be obtained. Further, according tothe present invention, an electrolyte membrane-electrode assembly usinga polymer electrolyte which has high proton conductivity and excellentdurability and exerts high performance, and a polymer electrolyte fuelcell constituted using the same can be obtained.

INDUSTRIAL APPLICABILITY

By combining the electrolyte membrane-electrode assembly obtained by theproduction method of the electrolyte membrane-electrode assembly for thepolymer electrolyte fuel cell of the present invention with a separator,a current corrector, an end plate, a fastening rod, a manifold and thelike, following the conventional method, a polymer electrolyte fuel cellexcellent in cell characteristics can be obtained.

1. A production method of an electrolyte membrane-electrode assembly fora polymer electrolyte fuel cell, comprising: a gas diffusion electrodehaving a gas diffusion layer and a catalyst layer; and a hydrogenion-conductive polymer electrolyte membrane bonded to said gas diffusionelectrode, said method being characterized by comprising: a step offorming a hydrogen ion-conductive polymer electrolyte membrane on a basematerial; a treatment step of reducing adhesion force between said basematerial and said hydrogen ion-polymer electrolyte membrane; a step ofseparating and removing said base material; and a step of bonding acatalyst layer and a gas diffusion layer onto said hydrogenion-conductive polymer electrolyte membrane.
 2. The production method ofan electrolyte membrane-electrode assembly for a polymer electrolytefuel cell in accordance with claim 1, wherein said forming stepcomprises a step of transfer-printing said hydrogen ion-conductivepolymer electrolyte membrane at least one time, and said hydrogenion-conductive polymer electrolyte membrane is supported by said basematerial until an electrolyte membrane-electrode assembly is obtained.3. The production method of an electrolyte membrane-electrode assemblyfor a polymer electrolyte fuel cell in accordance with claim 1,comprising: a step (1) of forming a hydrogen ion-conductive polymerelectrolyte membrane on a first base material and a second basematerial; a step (2) of forming a catalyst layer on said hydrogenion-conductive polymer electrolyte membrane formed on said basematerial; a step (3) of attaching by pressure and bonding a gasket and agas diffusion layer onto said hydrogen ion-conductive polymerelectrolyte membrane and said catalyst layer on said base material; astep (4) of separating and removing said base material to obtain a firstsemi-assembly and a second-semi assembly; and a step (5) of attaching bypressure said first semi-assembly to said second semi-assembly whilesaid hydrogen ion-conductive polymer electrolyte membranes thereof aremutually opposed to obtain an electrolyte membrane-electrode assembly,wherein said method further comprises, between said steps (1) and (4), atreatment step of reducing adhesion force between said base material andsaid hydrogen ion-conductive polymer electrolyte membrane.
 4. Theproduction method of an electrolyte membrane-electrode assembly for apolymer electrolyte fuel cell in accordance with claim 1, comprising: astep (I) of forming a catalyst layer on a first base material and asecond base material; a step (II) of forming a hydrogen ion-conductivepolymer electrolyte membrane on said catalyst layer such that saidmembrane covers said catalyst layer formed on said base material and onthe periphery of said catalyst layer; a step (III) of attaching bypressure said first base material to said second base material whilesaid hydrogen ion-conductive polymer electrolyte membranes thereof aremutually opposed to obtain a pre-assembly; a step (IV) of separating andremoving said first base material from said pre-assembly; a step (V) ofattaching by pressure a gas diffusion layer and a gasket onto saidcatalyst layer and said hydrogen ion-conductive polymer electrolytemembrane which are exposed by said step (IV); a step (VI) of separatingand removing said second base material from said pre-assembly; and astep (VII) of attaching by pressure a gas diffusion layer and a gasketonto said catalyst layer and said hydrogen ion-conductive polymerelectrolyte membrane which are exposed by said step (VI) to obtain anelectrolyte membrane-electrode assembly, wherein said method comprises,between said steps (II) and (IV) and/or said steps (IV) and (VII), atreatment step of reducing adhesion force between said base material andsaid hydrogen ion-conductive polymer electrolyte membrane.
 5. Theproduction method of an electrolyte membrane-electrode assembly for apolymer electrolyte fuel cell in accordance with claim 1, wherein saidstep of forming a hydrogen ion-conductive polymer electrolyte membraneon a base material is a step of transfer-printing a hydrogenion-conductive polymer electrolyte membrane formed on a base materialfor transfer-printing, to said base material.
 6. The production methodof an electrolyte membrane-electrode assembly for a polymer electrolytefuel cell in accordance with claim 1, wherein at least the surface ofsaid base material is constituted of a material which reduces theadhesion property to said hydrogen ion-conductive polymer electrolytemembrane by heating, or a material which evaporates or sublimates byheating, and said treatment step is a step of heating said basematerial.
 7. The production method of an electrolyte membrane-electrodeassembly for a polymer electrolyte fuel cell in accordance with claim 1,wherein at least the surface of said base material is constituted of amaterial which reduces the adhesion property to said hydrogenion-conductive polymer electrolyte membrane by cooling, and saidtreatment step is a step of cooling said base material.
 8. Theproduction method of an electrolyte membrane-electrode assembly for apolymer electrolyte fuel cell in accordance with claim 1, wherein atleast the surface of said base material is constituted of a materialwhich reduces the adhesion property to said hydrogen ion-conductivepolymer electrolyte membrane by irradiating active light rays, or amaterial which evaporates or sublimates by irradiating active lightrays, and said treatment step is a step of irradiating said basematerial with active light rays.
 9. The production method of anelectrolyte membrane-electrode assembly for a polymer electrolyte fuelcell in accordance with claim 1, wherein said base material comprises onthe surface thereof an adhesion layer capable of dissolving in asolvent, and said treatment step is a step of bringing said basematerial in contact with a solvent.
 10. The production method of anelectrolyte membrane-electrode assembly for a polymer electrolyte fuelcell in accordance with claim 1, wherein said treatment step is a stepof depressurizing or pressurizing the face opposite to the face of saidbase material with said hydrogen ion-conductive polymer electrolytemembrane formed.
 11. The production method of an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with claim 1, wherein said method comprises a step ofarranging a reinforcing film made of a frame-shaped hydrogenion-conductive film or gas diffusive film between said hydrogenion-conductive polymer electrolyte membrane and said catalyst layer,between said catalyst layer and said gas diffusion layer or between saidhydrogen ion-conductive polymer electrolyte membranes, in a clearancebetween said gasket and said gas diffusion electrode.
 12. A productionmethod of an electrolyte membrane-electrode assembly for a polymerelectrolyte fuel cell, said electrolyte membrane-electrode assemblyhaving: a hydrogen ion-conductive polymer electrolyte membrane; and agas diffusion electrode which contains a catalyst layer and a gasdiffusion layer and is bonded to both faces of said hydrogenion-conductive polymer electrolyte membrane, said method beingcharacterized by comprising: a step of bonding a hydrogen ion-conductivepolymer electrolyte membrane and a catalyst layer via a coating layerpositioned between the membrane and the catalyst layer; a step ofremoving said coating layer; and a step of obtaining an electrolytemembrane-electrode assembly by forming a gas diffusion layer on saidcatalyst layer.
 13. The production method of an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with claim 12, wherein said method comprises: a step (a1) offorming a coating layer on a catalyst layer; a step (b1) of applying ahydrogen ion-conductive polymer electrolyte solution onto said coatinglayer; a step (c1) of removing said coating layer to obtain anelectrolyte membrane-catalyst layer assembly; and a step (d1) of forminga gas diffusion layer on said catalyst layer.
 14. The production methodof an electrolyte membrane-electrode assembly for a polymer electrolytefuel cell in accordance with claim 12, wherein said method comprises: astep (a2) of forming a hydrogen ion-conductive polymer electrolytemembrane on the coating layer which comprises a polymer film; a step(b2) of arranging said catalyst layer on said polymer film; a step (c2)of removing said polymer film to obtain an electrolyte membrane-catalystlayer assembly; and a step (d2) of forming said gas diffusion layer onsaid catalyst layer.
 15. A production method of an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cellcomprising: a first step of applying on a catalyst layer a coating layerraw material solution containing a hydrogen ion-conductive polymerelectrolyte and a solvent, to form a liquid layer; a second step ofdrying said liquid layer to remove said solvent to form a gelated layer;a third step of drying said gelated layer to be solidified to form acoating layer; a fourth step of applying on said coating layer a polymerelectrolyte membrane raw material solution to form a polymer electrolytemembrane; a fifth step of forming a gas diffusion layer on a side ofsaid catalyst layer, where said coating layer is not formed, to form anassembly in which at least said catalyst layer is disposed between saidpolymer electrolyte membrane and said gas diffusion layer; and a sixthstep of heating said assembly to form an electrolyte membrane-electrodeassembly.
 16. The production method of an electrolyte membrane-electrodeassembly for a polymer electrolyte fuel cell in accordance with claim15, wherein a concentration of said hydrogen ion-conductive polymerelectrolyte in said gelated layer formed in said second step is 10 to 20wt %.
 17. The production method of an electrolyte membrane-electrodeassembly for a polymer electrolyte fuel cell in accordance with claim15, wherein said second step is repeated plural times before said thirdstep.
 18. The production method of an electrolyte membrane-electrodeassembly for a polymer electrolyte fuel cell in accordance with claim15, wherein said gelated layer is solidified at a temperature of 100 to140° C. in said third step.
 19. The production method of an electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with claim 15, wherein said coating layer is integrated insaid polymer electrolyte membrane in said electrolyte membrane-electrodeassembly obtained after said sixth step.
 20. An electrolytemembrane-electrode assembly for a polymer electrolyte fuel cellcomprising: a polymer electrolyte membrane; and a pair of electrodesarranged on both sides of said polymer electrolyte membrane, at leastone of said pair of electrodes including a catalyst layer and a gasdiffusion layer, said catalyst layer including a mixture containing: acatalyst body; a first polymer electrolyte; and a polyfunctional basiccompound, said catalyst body including a noble metal catalyst and acarbon powder, wherein said first polymer electrolyte has two or moresulfonic acid groups, parts of said sulfonic acid groups and saidpolyfunctional basic compound are bonded, said polyfunctional basiccompound is a polyfunctional amine, said catalyst layer contains from0.1 to 10 wt % of said polyfunctional basic compound with respect tosaid first polymer electrolyte, and the main chain of saidpolyfunctional basic compound is fluorinated.
 21. The electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with claim 20 , wherein said part of said sulfonic acidgroups and said polyfunctional basic compound are bonded together byionic bonding.
 22. An electrolyte membrane-electrode assembly for apolymer electrolyte fuel cell comprising: a polymer electrolytemembrane; and a pair of electrodes arranged on both sides of saidpolymer electrolyte membrane, at least one of said pair of electrodesincluding a catalyst layer and a gas diffusion layer, said polymerelectrolyte membrane containing: a second polymer electrolyte; and apolyfunctional basic compound, wherein said second polymer electrolytehas two or more sulfonic acid groups, parts of said sulfonic acid groupsand said polyfunctional basic compound are bonded, said polyfunctionalbasic compound is a polyfunctional amine, and the main chain of saidpolyfunctional basic compound is fluorinated.
 23. The electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with claim 22 , wherein said polymer electrolyte membranecontains from 0.1 to 10 wt % of said polyfunctional basic compound withrespect to said second polymer electrolyte.
 24. The electrolytemembrane-electrode assembly for a polymer electrolyte fuel cell inaccordance with claim 22 , wherein said part of said sulfonic acidgroups and said polyfunctional basic compound are bonded together byionic bonding.
 25. An electrolyte membrane for a polymer electrolytefuel cell comprising: a polymer electrolyte and a polyfunctional basiccompound, wherein the polymer electrolyte has two or more sulfonic acidgroups, parts of said sulfonic acid groups and said polyfunctional basiccompound are bonded, said polyfunctional basic compound is apolyfunctional amine, and the main chain of said polyfunctional basiccompound is fluorinated.
 26. The electrolyte membrane for a polymerelectrolyte fuel cell in accordance with claim 25, containing from 0.1to 10 wt % of said polyfunctional basic compound with respect to saidpolymer electrolyte.
 27. The electrolyte membrane for a polymerelectrolyte fuel cell in accordance with claim 25, wherein said part ofsaid sulfonic acid groups and said polyfunctional basic compound arebonded together by ionic bonding.